1. Field of the Invention
The present invention relates to a technical field of an image change detecting apparatus, an image change detecting method, an image encoding apparatus, and an information recording medium having an image change detecting program recorded in a computer readable manner. More particularly, the present invention relates to a technical field of the image change detecting apparatus and method for detecting whether or not a fade change occurs, in which an image constituent element continuously changes so that it gradually appears from a field image composed of a single color up to a field image containing any image constituent element among a plurality of continuous field images in image information. Further, the present invention relates to the image encoding apparatus containing the same and the information recording medium having the program recorded in a computer readable manner for detecting the above-mentioned image change.
2. Description of the Related Art
In general, in the case of encoding (including compression encoding) image information having a plurality of continuous frame images composed of two or more field images, it is required to optimally control an encoding parameter according to characteristics of the image information.
An MPEG (Moving Picture Experts Group) system is generally known as the above encoding system recently.
This MPEG system is a kind of encoding processing using a discrete cosine transform (DCT) system. In recent years, the MPEG system is defined as an international standard for a system of encoding image information (including both of moving image information and static image information) with high efficiency, that is, for a compression encoding system.
In image compression encoding using the MPEG system, generally, an original image to be compressed and encoded is divided into a block called macro-block as pixel block. The macro-block includes 16×16 pixels out of the original image composed of a plurality of pixels. Then, motion compensation and the DCT, or encoding processing are executed in unit of the macro block.
On the other hand, the image information to be encoded may include fade change in which any image constituent element continuously changes so that it gradually appears from a field image composed of a single color (any color is acceptable.) up to a field image including any image constituent element among a plurality of continuous field images. For example, the fade change denotes a change that a cloud gradually appears in the sky. In this case, the fade change is called “fade-in”.
If an occurrence of the fade change is detected, it is required to set the parameter after the occurrence so that the parameter is suitable to a field image after any image constituent element appeared. In the case where the field image is encoded after any image constituent element appeared by using the parameter suitable for a field image composed of a single color without setting the parameter as mentioned above, there occurs a failure such as interfusion of a variety of noises in the image reproduced for a predetermined period immediately after fade change occurred when the encoded image information is decoded and reproduced.
However, in a conventional MPEG system, the above described fade change is not detected.
Therefore, in image encoding using the conventional MPEG system, there has been a problem that a variety of noises are interfused in the decoded image after the fade change occurred.